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BONUS RETURN
Reducing Emissions by Turning Nutrients and Carbon into
Benefits
https://www.bonusprojects.org/bonusprojects/the_projects/blue_baltic_projects/return
www.bonusreturn.eu
Deliverable No: D.3.3 – Report from the multi-criteria analysis
from workshop 2 with comparisons of the different alternatives in
each case study and selection of eco-technologies for further use
in
WP5 Ref: WP (3) Task (3.3) Lead participant: RISE
Date: 15/04/2019
BONUS RETURN has received funding from BONUS (Art 185), funded
jointly by the EU and Swedish Foundation for Strategic
Environmental Research FORMAS, Sweden’s innovation agency VINNOVA,
Academy of Finland and National Centre for Research and Development
in Poland. This document contains information proprietary of the
BONUS RETURN consortium. Neither this document nor the information
contained herein shall be used, duplicated or communicated by any
means to any third party, in whole or in part, except with the
prior written consent of the BONUS RETURN coordinator.
https://www.bonusprojects.org/bonusprojects/the_projects/blue_baltic_projects/return
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Deliverable Title D.3.3 – Report from the multi-criteria
analysis from
workshop 2 with comparisons of the different
alternatives in each case study and selection of eco-
technologies for further use in WP5
Filename BONUSRETURN_D.3.3_Report from the multi-criteria
analysis
Authors Solveig Johannesdottir (RISE), Erik Kärrman (RISE),
Emelie
Ljung (RISE), Christina Anderzén (RISE), Mats Edström
(RISE), Serina Ahlgren (RISE), Maja Englund (RISE)
Contributors Olle Olsson (SEI), Marek Giełczewski (WULS), Jari
Koskiaho
(SYKE), Sirkka Tattari (SYKE), Marcus Ahlström (RISE),
Daniel Tamm (RISE), Turo Hjerppe (SYKE), Sari Väisänen
(SYKE), Mikołaj Piniewski (WULS)
Date 15/04/2019
Start of the project: 01/05/2017
End of the project: 01/05/2020
Project coordinator: Stockholm Environment Institute (SEI)
Dissemination level
x PU Public.
PP Restricted to other project partners.
RE Restricted to a group specified by the consortium.
CO Confidential, only for members of the consortium.
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Table of Contents
Executive Summary ………………………………………………………………………………………………………….…. 1
1 Introduction
....................................................................................................................................
8
1.1 Project Objectives
....................................................................................................................
8
1.2 Project Structure
...................................................................................................................
10
1.1 Deliverable context and objective
.........................................................................................
10
1.2 Outline of the report
.............................................................................................................
10
2 Report from the multi-criteria analysis from workshop 2 with
comparisons of the different alternatives in each case study and
selection of ecotechnologies for further use in WP5
.................. 11
2.1 General method
....................................................................................................................
11
2.1.1 Selection of sustainability criteria and system
alternatives .......................................... 12
2.2 The Vantaanjoki catchment area
..........................................................................................
13
2.2.1 First workshop
...............................................................................................................
14
2.3 The Fyrisån catchment area
..................................................................................................
14
2.3.1 First workshop
...............................................................................................................
15
2.4 The Słupia catchment area
....................................................................................................
15
2.4.1 First workshop
...............................................................................................................
15
2.5 General learning points and issues
.......................................................................................
16
2.6 Assessment of the sustainability criteria
...............................................................................
16
3 Multi-criteria analysis in the Vantaanjoki case
.............................................................................
20
3.1 System alternatives
...............................................................................................................
20
3.1.1 System alternative 1:
Composting.................................................................................
20
3.1.2 System alternative 2: Anaerobic digestion
....................................................................
22
3.1.3 System alternative 3: Pyrolysis + urea-hygienization of
source-separated blackwater 23
3.2 System boundaries and assumptions
....................................................................................
25
3.3 Results
...................................................................................................................................
26
3.3.1 Global warming potential
..............................................................................................
26
3.3.2 Total costs
......................................................................................................................
27
3.3.3 Eutrophication potential
...............................................................................................
28
3.3.4 Nutrient recovery
..........................................................................................................
28
3.3.5 Risk of exposure to pollutants
.......................................................................................
29
3.3.6 Effects on soil structure
.................................................................................................
30
3.3.7 Acceptance of using recycled fertilizer products
.......................................................... 30
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3.3.8 Local economy
...............................................................................................................
30
3.3.9 Compatibility with existing infrastructure
.....................................................................
30
3.3.10 Second workshop in Vantaanjoki
..................................................................................
31
3.3.11 Sustainability scores for all systems
..............................................................................
31
3.4 Discussion of results
..............................................................................................................
33
3.5 Conclusions
............................................................................................................................
34
4 Multi-criteria analysis in the Fyrisån
case.....................................................................................
35
4.1 System alternatives
...............................................................................................................
35
4.1.1 Alt 0F Baseline
...............................................................................................................
35
4.1.2 Alt 1F Incineration
.........................................................................................................
36
4.1.3 Alt 2F Nutrient extraction
..............................................................................................
37
4.1.4 Alt 3F Source-separation
...............................................................................................
38
4.2 System boundaries and assumptions
....................................................................................
39
4.3 Results
...................................................................................................................................
41
4.3.1 Global warming potential, eutrophication potential and
nutrient recovery ................ 41
4.3.2 Risk of exposure to pollutants
.......................................................................................
44
4.3.3 Total costs
......................................................................................................................
45
4.3.4 Technical robustness
.....................................................................................................
46
4.3.5 Technical flexibility
........................................................................................................
47
4.3.6 Second workshop in Fyris
..............................................................................................
47
4.3.7 Sustainability scores for all systems
..............................................................................
48
4.4 Discussion of results
..............................................................................................................
50
4.4.1 Assessment of criteria
...................................................................................................
50
4.4.2 Scoring and weighting
...................................................................................................
52
4.5 Conclusions
............................................................................................................................
53
5 Multi-criteria analysis in the Słupia case
......................................................................................
54
5.1 System alternatives
...............................................................................................................
54
5.1.1 Alt 0S Baseline
...............................................................................................................
54
5.1.2 Alt 1S Reject water
........................................................................................................
55
5.1.3 Alt 2S Nutrient extraction
..............................................................................................
55
5.1.4 Alt 3S Source-separation
...............................................................................................
56
5.2 System boundaries and assumptions
....................................................................................
57
5.3 Results
...................................................................................................................................
59
5.3.1 Global warming potential, eutrophication potential and
nutrient recovery ................ 59
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5.3.2 Total costs
......................................................................................................................
61
5.3.3 Risk of exposure to pollutants
.......................................................................................
62
5.3.4 Technical robustness
.....................................................................................................
63
5.3.5 Technical flexibility
........................................................................................................
64
5.3.6 Second workshop in Słupia
............................................................................................
64
5.3.7 Sustainability scores for all systems
..............................................................................
65
5.4 Discussion of results
..............................................................................................................
67
5.4.1 Assessment of criteria
...................................................................................................
67
5.4.2 Scoring and weighting
...................................................................................................
68
5.5 Conclusions
............................................................................................................................
69
6 Discussion and
conclusions...........................................................................................................
70
7 References
....................................................................................................................................
71
8 Appendix – Review of sustainability
criteria.................................................................................
73
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EXECUTIVE SUMMARY In this report, sustainability assessments of
different potential systems for recovering and reusing nutrients
and carbon (organic matter and energy) from different wastes are
presented. The assessments were done in three different
case-studies: the Vantaanjoki catchment area in Finland, the Fyriså
catchment area in Sweden and the Słupia catchment area in Poland. A
sustainability analysis approach with multi-criteria analysis (MCA)
was used to assess different system alternatives in the three case
studies. A review of sustainability criteria was used as the
starting point for selection of criteria. Systematic maps of
ecotechnologies for the recovery and reuse of nutrients and carbon
within the Baltic Sea region were used as the basis for selection
of technological system components and overall system alternative
design. Two workshops were held in each case study. The aim of the
first workshop was to gain insights into the local contexts,
challenges, opportunities and stakeholders’ interests. Knowledge
gained from the workshop influenced the selection of sustainability
criteria and system alternatives. At the second workshop, the
stakeholders were asked to assign weights to the different criteria
according to their relative importance. Each system alternative was
evaluated for each sustainability criteria and the overall
sustainability score was calculated as the weighted sum of criteria
scores and weights. For the Vantaanjoki case study, different
systems for managing horse manure, waste-grass and source-separated
blackwater from scattered settlements were assessed. The system
alternatives evaluated were 1. Composting (baseline system
representing current management), 2. Anaerobic digestion and 3.
Pyrolysis + urea hygienization of source-separated blackwater.
These systems were evaluated against the 9 criteria: global warming
potential, eutrophication potential, nutrient recovery, effects on
soil structure, total costs, local economy, risk of exposure to
pollutants, acceptance and compatibility with existing
infrastructure. The system anaerobic digestion system alternative
got the highest sustainability score, although the Pyrolysis + urea
hygienization got an only slightly lower score. Both systems
received higher sustainability scores than the composting
alternative. For both the Fyriså and the Słupia case studies
nutrient recovery from domestic wastewater was assessed. The same 8
sustainability criteria were used for both case-studies: global
warming potential, eutrophication potential, nutrient recovery,
total costs, risk of exposure to pollutants, acceptance, technical
robustness and technical flexibility. For the Fyriså case study,
four system alternatives were evaluated: 0. Baseline system
(representing current management), 1. Incineration of sludge and
phosphorus extraction from ash 2. Anaerobic treatment in
UASB-reactor and nutrient extraction through ammonia stripping and
struvite recovery and 3. Source-separation (blackwater treated as
in 2. and sludge treated as in 1.). The source-separation system
got the highest score, followed by the nutrient extraction system
and incineration system. All recovery systems received a higher
sustainability score than the baseline system. In the Słupia case
study, four similar system alternatives were evaluated; 0. Baseline
system (representing current management), 1. Ammonia stripping from
reject water from dewatering anaerobic digestate 2. Anaerobic
treatment in UASB-reactor and nutrient extraction through ammonia
stripping and struvite recovery and 3. Source-separation
(blackwater treated as in 2.) in all systems
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sludge was composted. The system alternative with nutrient
extraction (2) got considerably higher score than the other systems
and source-separation got the lowest, compared to the baseline
system. Results showed that the source-separation system could
receive a sustainability score lower than the baseline system. The
outcome of the assessment was different for the Fyriså and Słupia
cases, even though the system alternatives were composted of
largely the same ecotechnologies. This shows that local context and
stakeholder participation are important parts of sustainability
assessments.
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1 INTRODUCTION
The degradation of the Baltic Sea is an ongoing problem, despite
investments in measures to reduce external inputs of pollutants and
nutrients from both diffuse and point sources. Available
technological and management measures to curb eutrophication and
pollution flows to the sea have not been adapted adequately to the
contexts in which they are being applied. Furthermore, measures are
often designed based on single objectives, thereby limiting
opportunities for multiple benefits. In addition, there is a
general sense that measures to address the deterioration of the
Baltic ecosystem are primarily technologically-driven and lacking
broader stakeholder acceptance – the “experts” who define these
measures have little engagement with industry, investors, civil
society and authorities. This problem is magnified by governance
and management, taking place in sectoral silos with poor
coordination across sectors. As a result, research shows that
regional institutional diversity is presently a barrier to
transboundary cooperation in the Baltic Sea Region (BSR) and that
actions to achieve national environmental targets can compromise
environmental goals in the BSR (Powell et al., 2013). The regional
dimension of environmental degradation in the BSR has historically
received weaker recognition in policy development and
implementation locally. However, developments in recent years
suggest a new trend with growing investments in environmental
protection supporting social, economic, and territorial cohesion.
The BSR is an environmentally, politically and economically
significant region and like other regions globally, its rapid
growth needs to be reconciled with the challenges of sustainable
development in a global setting that demands unprecedented
reductions in GHG emissions. This poses a truly wicked problem
exacerbated by the fact that many of the challenges in the BSR will
also magnify in a changing climate. In order to navigate the
uncertainties and controversies associated with a transformation
towards a good marine environment, BONUS RETURN will enact an
innovative trans disciplinary approach for identifying and piloting
systemic eco-technologies. The focus is on eco-technologies that
generate co-benefits within other interlinked sectors, and which
can be adapted according to geophysical and institutional contexts.
More specifically, emphasis is placed on eco-technologies that
reconcile the reduction of present and future eutrophication in
marine environments with the regional challenges of policy
coherence, food security, energy security, and the provision of
ecosystem services.
1.1 Project Objectives
The overall aim of BONUS RETURN is to improve the adaptation and
adoption of eco-technologies in the Baltic Sea Region for maximum
efficiency and increased co-benefits. The specific objectives of
the project can be divided into six categories presented below.
These categories are interlinked but for the purpose of providing a
step-wise description, the following overview of each category
proves useful. BONUS RETURN is:
1) Supporting innovation and market uptake of eco-technologies
by:
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- Contributing to the application and adaptation of
eco-technologies in the BSR through an evidence-based review
(systematic map) of the developments within this field.
- Contributing to the development of emerging eco-technologies
that have the capacity to turn nutrients and carbon into benefits
(e.g. bio-energy, fertilizers), by providing an encompassing
framework and platform for rigorous testing and analysis.
- Developing decision support systems for sustainable
eco-technologies in the BSR. - Contributing to better assessment of
eco-technology efficiency via integrated and
participatory modelling in three catchment areas in Finland,
Sweden and Poland. - Contributing to methodological innovation on
application and adaptation of eco-technologies.
2) Reducing knowledge gaps on policy performance,
enabling/constraining factors, and costs
and benefits of eco-technologies by: - Assessing the broader
socio-cultural drivers linked to eco-technologies from a
historical
perspective. - Identifying the main gaps in the policy
environment constraining the implementation of
emerging eco-technologies in the catchments around the Baltic
Sea. - Informing policy through science on what works where and
under which conditions through
an evidence-based review (systematic map and systematic reviews)
of eco-technologies and the regional economic and institutional
structures in which these technologies evolve.
3) Providing a framework for improved systematic stakeholder
involvement by: - Developing methods for improved stakeholder
engagement in water management through
participatory approaches in the case study areas in Sweden,
Finland and Poland. - Enacting a co-enquiry process with
stakeholders into opportunities for innovations in eco-
technologies capable of transforming nutrients and pollutants
into benefits for multiple sectors at different scales.
- Bringing stakeholder values into eco-technology choices to
demonstrate needs for adaptation to local contexts and ways for
eco-technologies to efficiently contribute to local and regional
developments.
- Disseminating results and facilitating the exchange of
learning experiences, first within the three catchment areas, and
secondly across a larger network of municipalities in the BSR.
- Establishing new cooperative networks at case study sites and
empowering existing regional networks by providing information,
co-organizing events and engaging in dialogues.
4) Supporting commercialization of eco-technologies by: -
Identifying market and institutional opportunities for
eco-technologies that (may) contribute
to resource recovery and reuse of nutrients, micro-pollutants
and micro-plastics (e.g. renewable energy).
- Identifying potential constraints and opportunities for
integration and implementation of eco-technologies using economical
models.
- Facilitating the transfer of eco-technologies contributing to
win-win solutions to multiple and interlinked challenges in the
BSR.
- Linking producers of eco-technologies (small and medium
enterprises – SMEs), to users (municipalities) by providing
interactive platforms of knowledge exchange where both producers
and users have access to BONUS RETURN’s envisaged outputs, existing
networks, and established methodologies and services.
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5) Establishing a user-driven knowledge platform and improved
technology-user interface by: - Developing an open-access database
that maps out existing research and implementation of
eco-technologies in the BSR. This database will be intuitive,
mapped out in an interactive geographical information system (GIS)
platform, and easily managed so that practitioners, scientists and
policy-makers can incorporate it in their practices.
- Developing methodologies that enact the scaling of a systemic
mix of eco-technological interventions within the highly diverse
contexts that make up the BSR and allows for a deeply interactive
medium of knowledge.
1.2 Project Structure
BONUS RETURN is structured around six Work Packages that will be
implemented in three river basins: The Vantaanjoki river basin in
Finland, the Słupia river basin in Poland, and Fyrisån river basin
in Sweden. Work Package 1: Coordination, management, communication
and dissemination. Work Package 2: Integrated Evidence-based review
of eco-technologies. Work Package 3: Sustainability Analyses. Work
Package 4: Environmental Modelling. Work Package 5: Implementation
Support for Eco-technologies. Work Package 6: Innovative Methods in
Stakeholder Engagement.
1.1 Deliverable context and objective
The current deliverable (Del. No 3.3) is part of WP (3). The
objectives of WP (3) are to evaluate sustainability aspects of
eco-technologies selected from WP2 using a decision support-based
framework for sustainability analysis for each catchment area. The
application of sustainability analysis includes a step-wise systems
analysis approach to be carried out together with local
stakeholders by: 1) defining system boundaries; 2) selecting
criteria covering health and hygiene, environmental issues,
economy, socio-cultural dimensions and technical function; 3)
selecting and formulating different system alternatives based on
the review of eco-technologies from WP2; 4) comparing the different
options using the criteria from step 2. The comparison is done by
using substance flow-, cost- effectiveness and cost benefit
analysis, energy analysis and qualitative assessments. In step 4, a
multi-criteria analysis is used for an integrated assessment of all
dimensions to reach a complete decision support system for
municipalities or regions. A second objective of WP3 is to identify
upcoming innovations for reuse (TRL 5 or higher), using the same
sustainability criteria as above. The final results of WP3 are a
selection of interesting eco-technologies for further development
in WP5. This deliverable summarizes the multi-criteria analysis
performed, including description of the system alternatives,
sustainability criteria chosen and results of the analysis for each
of the three case-studies.
1.2 Outline of the report
This report is structured as follows: first, the general method
used is presented together with a short description of the
catchment areas and main learning points from the first scoping
workshop held in
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each. Then, the framework and results of the analysis are
presented for each case study separately, starting with Vantaanjoki
(Finland) followed by Fyrisån (Sweden) and Słupia (Poland). Lastly,
a general discussion and final conclusions are made.
2 REPORT FROM THE MULTI-CRITERIA ANALYSIS FROM WORKSHOP 2 WITH
COMPARISONS OF
THE DIFFERENT ALTERNATIVES IN EACH CASE STUDY AND SELECTION OF
ECOTECHNOLOGIES
FOR FURTHER USE IN WP5
2.1 General method
A sustainability analysis approach with multi-criteria analysis
(MCA) was used to assess the different alternatives in the three
case studies. This approach was mainly based on Strategic Planning
of Sustainable Urban Water Management (Malmqvist et al., 2006) and
consists of the 8 steps: 1) Goal and scope definition, 2) Selection
of criteria, 3) Selection of alternatives, 4) Analysis and
evaluation, 5) Scoring, 6) Weighting 7) Interpretation of results
and 8) Sensitivity analysis. This MCA-approach has been applied as
decision support in more than 20 applications for urban and rural
water, wastewater and solid waste management. For the BONUS RETURN
project, we have used this general method of MCA. The selection of
criteria started with a literature review of criteria (see
Appendix). Stakeholder engagement in the selection was included
through a first workshop in each case study (see 2.2.1, 2.3.1 and
2.4.1). The criteria chosen for the assessment is the basis of the
sustainability evaluation. Each system alternative chosen is
assessed regarding its performance based on the criterion in
question. Depending on its performance, it is given a
representative score. In this way, the system alternatives are
compared to each other in respect to the chosen sustainability
aspects. The selection of system alternatives started with the
selection of which sector to focus on in each case study. The
sectors relevant for the project were agricultural and wastewater.
In both sectors, the focus would be on the sustainability of
managing resources from wastes in a different way than current
practice. In the agricultural sector, a typical resource could be
manure whilst in the wastewater sector it would be domestic
wastewater. The management of these resources is the function of
the system and could include different ecotechnologies in various
constellations. Furthermore, aspects of sustainability not only
apply to the part where nutrients or carbon are extracted, but also
before and after those steps. For example, collection and transport
of manure is a source of both emissions and costs and should
therefore be accounted for in the system. The same goes for
transport of the product to the site where nutrients will be
reused; different technologies could produce products of different
densities leading to differences in emissions from transport. The
system therefore consists of both collection, treatment and reuse
of substrates and products. In order to make a comparison between
the different systems, they all need to perform the same net
function. If a certain amount of substrate is managed in one
system, the same amount needs to be managed in some way in all the
compared systems, otherwise they are not comparable. Furthermore,
in order for the system to provide adequate functions, additional
system components such as conventional management practices may
need to be included. This could, for example, be additional,
conventional treatment of wastewater after nutrients have been
extracted in order to limit eutrophication.
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There can be many different external inputs to the systems that
have emissions, costs or other sustainability aspects accompanying
them. Such external inputs can be electricity and chemicals. These
resources need to be accounted for when comparing the systems,
since they consume different amounts. This is done by adding e.g.
the emissions from production of the amount of electricity needed
in the system, even though electricity production is not included
as an internal function of the studied system.
2.1.1 Selection of sustainability criteria and system
alternatives
For all case studies, the same general method was used to
conduct the sustainability assessment (see above). Two workshops
were held in each case study. The aim of the first workshop was to
gain insights into the local contexts, challenges, opportunities
and stakeholders’ interests. This was done during a one-day
workshop with local stakeholders which included presentations of
the BONUS RETURN project and group exercises to identify and
discuss relevant sustainability criteria and eco-technologies for
the area. The progress of the systematic mapping from WP2 (see
Haddaway (2018)) was presented, as well as a list of example
sustainability criteria. Since it was uncertain which sector,
whether agriculture or wastewater, would be the focus of the study
in the sites, a general list of sustainability criteria was used.
The criteria are divided into five categories: environmental,
economic, socio-cultural, health and hygiene, and technical
function. Each category includes several criteria, as outlined in
Table 1. Table 1. Sustainability criteria presented as examples to
stakeholders at the first workshops.
Environmental Economic Socio-cultural Health & hygiene
Technical function
Climate effect Life cycle cost Acceptance Work environment
Flexibility
Reuse of resources Capital/investment costs
Laws and policy Health risks Reliability
Emission of pollutants
Work force demands
Encourage sustainability
Pathogens Technical complexity
Biodiversity Economic vulnerability
Cultural and aesthetic values
Toxic substances Lifetime
Land use Quality of products Functioning organization
Compatibility with existing infrastructure/technology
Use of resources (energy, water etc.)
Support local economy
Equity Maintenance requirement
The criteria in each category identified as most relevant by the
stakeholders were given priority in the final selection of criteria
for the assessment. However, consideration of the suitability of
the criteria to the scope of the assessment and system alternatives
had to be considered. Criteria representing aspects that are not
accounted for in the system alternatives are of no use. For
practical reasons the
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aim was to have at most 10 criteria to assess across all
categories. To maximize the usefulness of the assessment, redundant
criteria were excluded. Therefore, the selection of criteria was
done in relation to the selection of system alternatives. The
selection of specific ecotechnologies to be included in the
different systems was primarily influenced by the systematic
mapping done in WP2 (see Macura et al. (2018)) and the first
workshop for each case study. Initially, the most common
ecotechnologies found in the maps were screened for relevance to
the case studies and compared in relation to the lessons learned
from the first workshops. These ecotechnologies, most of which can
be applied in both wastewater and agriculture sector, were the
following:
• Anaerobic treatment (biogas production)
• Adsorption of nitrogen and/or phosphorus
• Composting
• Biomass production for energy or biofuel production
• Irrigation with treated wastewater
• Hydrothermal treatment
• Membrane filtration
• Microalgae cultivation
• Microbial fuel/electrolysis cells
• Ammonia stripping
• Struvite recovery
• Pyrolysis and biochar use
• Source-separation of wastewater
• Vermicomposting
Next, the relevant ecotechnologies were evaluated based on the
feasibility of assessing them with the sustainability assessment
framework used and the accessibility of data for modelling. The
resource recovery technologies chosen from the maps were
complemented as needed with conventional technologies, so that the
systems would function adequately. An initial suggestion of
sustainability criteria and system alternatives was sent out to the
BONUS RETURN consortium for feedback. It was also sent to the
stakeholders who participated in the first workshop so they would
have a chance to give feedback. Based on the feedback received, the
suggestion was revised as needed. After the final criteria and
systems were chosen, further revisions were made only if problems
with data requirements or execution demanded it.
2.2 The Vantaanjoki catchment area
The Vantaanjoki River basin (1,680 km2) flows through the
Helsinki metropolitan area (ca. 1 million inhabitants) before
discharging into the Baltic Sea. The catchment area consists of 23%
agriculture, 56% forestry and 17% urban area. Over 90% of the
population is connected to a sewage network. The estimated number
of on-site treatments for wastewater is 10,000 households. Treated
sewage water from this region is discharged into the open sea area
in the Gulf of Finland. There are five municipal
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wastewater treatment plants, four of which discharge treated
wastewater into the river. The level of treatment at the municipal
plants is high, e.g. around 95% of the phosphorus in the wastewater
is removed during treatment. In the upper reaches of the river
there are two towns (Riihimäki and Hyvinkää) with their own
wastewater treatment plants also discharging treated wastewater
into the river. The Vantaanjoki River basin is characterized by a
variety of water resource problems, of which the most serious is
non-point source pollution from agricultural fields and the point
source pollution coupled with stormwater runoff from the urban
areas.
2.2.1 First workshop
The stakeholders identified several ecotechnologies they deemed
interesting for their catchment area. The ecotechnologies included
the following:
• Forestation/restoration of riparian areas for recreational
use, nutrient retention, etc.
• Increase in water-protection methods, e.g. naturalistic
drainage systems
• Consideration of water and protection of it in planning and
under construction
• Termination of wastewater overflow
• Production of biogas from grass, horse manure, manure and
other agricultural residues and
return nutrients to agriculture
• Maintaining fertility and soil structure of agricultural
lands, reducing nutrient loads
• Holistic management of drainage
• Source-separation of wastewater for scattered settlements,
greywater treated on-site and
blackwater stored and then transported to treatment plant where
it could be used in small-
scale cultivation after lime-stabilization. Concern about
transporting distances and
responsibility
• Water management in agriculture and forestry, e.g. water
retention on non-productive lands
• Management of leakages in urban stormwater network, biochar
improved infiltration, urban
wetlands
2.3 The Fyrisån catchment area
The Fyrisån River basin (1,982 km2) is located in the
south-eastern part of Sweden. The Fyrisån River is a tributary of
Lake Mälaren, which has its outlet through Stockholm into the
Baltic Sea. The catchment area is distributed among forests (60%),
agriculture (32%), wetlands (4%), lakes (2%) and urban areas (2%).
The urban area is dominated by the city of Uppsala, the fourth
largest city in Sweden, whose wastewater treatment plant discharges
treated wastewater into the river. The total number of people
living within the catchment area is difficult to assess since it
covers parts of 6 different municipalities. The Fyrisån River basin
covers a quite diverse set of landscapes. The water quality status
of the river has also been very well documented for a long time,
making it possible to e.g. trace effects of historical
implementations of ecotechnologies in wastewater treatment plants
in the basin. There are several smaller treatment plants, most
operated by municipal water companies. Around 83% of households are
estimated to be connected to a sewer network.
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2.3.1 First workshop
The following points were discussed by local stakeholders at the
scoping workshop:
• Increasing the buffering capacity (of water flow) in the
river, for example by introducing
productive wetlands
• Addressing the spreading of pathogens in smaller communities
(from small sewage systems)
• Activity-based actions, e.g. phosphorus capture
• Recovery at decentralized wastewater treatment plants, e.g. by
liquid composting, treatment
outdoors, wetlands
• Source-separated sewage at small and on-site treatment
systems
• Biochar production from forestry waste
• Reduce use of phosphorus chemical fertilizer by substituting
with sludge and other sources
of recovered phosphorus, such as from phosphorus traps at
fields
• Urine-diversion toilets
• Not connecting new residential areas to the central treatment
plant but instead building
decentralized treatment
• Membrane filtration of reject water from anaerobic digestion
to capture pharmaceuticals
• Pyrolysis of sewage sludge and use of the biochar as soil
improver, possibly mixed with
treated source-separated blackwater
• Reuse of treated wastewater for industry e.g. as cooling water
or for irrigation
• Recognize (gravity-based) combined sewers, employing drinking
water as transport medium
for excreta, as unsustainable
• Address the problem at source, not at the end of the pipe
2.4 The Słupia catchment area
The Słupia River basin (1,623 km2) is a diverse coastal
catchment with an expansive area of dunes stretching along the
coast. Agricultural land and forest represent 54% and 42% of the
basin, respectively. Urban areas constitute around 3%, of which the
largest portion is taken by the city of Słupsk with 95,000
inhabitants, and two smaller towns (Bytów and Ustka). All of them
have their own wastewater treatment plants discharging treated
wastewater into the Słupia River system. The Słupia catchment is
one of the largest catchments on the Polish coast that includes a
large city (Słupsk) and thus it offers a unique opportunity to
study the pressure on water quality from both rural and urban
areas, which are predominant in this part of the BSR.
2.4.1 First workshop
The following ecotechnologies and measures were discussed by
stakeholders in Słupia:
• Enhanced wastewater treatment level, e.g. through
ultrafiltration and UV-disinfection
• Mitigate agricultural nutrient emissions and improve
stormwater management, the second
being a problem due to increase in area that is paved
• Small retention reservoirs and river restoration for increased
self-purification
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• The awarded winners of the BR innovation competition
(Deliverable 3.7) concerned with
phosphorus recovery are interesting and seem implementable
• Either 100% of population are to be connected to wastewater
treatment plants, or on-site
treatment needs to be improved
• Improving the liming and drainage management on farms
• Increasing use of renewable energy
• Optimizing fertilization rates based on soil parameters using
geo-location systems
• Improved on-farm composting practices
• Crop rotation and optimization of livestock density for better
nutrient management
• Introduce micro-strainer technologies at fish farms to reduce
the environmental impact
• Increase environmental monitoring, both coverage and
parameters measured
2.5 General learning points and issues
There was no agreement about which sector, i.e. agriculture or
wastewater, that was most important to focus on in the context of
this MCA in any of the catchment areas. There is evidence that the
agricultural sector is a larger source of eutrophying emissions
than the wastewater sector (HELCOM, 2018). The agricultural
emissions are to a large extent diffuse, e.g. nutrient leaching
from arable lands. The aim of this assessment is to compare
different systems for recovering and reusing nutrients and carbon.
There have been few ecotechnologies identified by WP2 that recover
nutrients or carbon from diffuse sources in a form that is possible
to reuse. Measures for dealing with diffuse sources are for example
practices leading to better nutrient management and retention of
nutrients in the soil, such as reduced tillage, crop rotation or
cover crops. These measures do not provide a nutrient or carbon
product that can be reused. In WP5, however, the awarded
eco-innovation, BioPhree, is designed to capture and recycle
nutrients from receiving waters so in the future also this type of
ecotechnology could be included in MCAs. But here the focus was on
wastewater and agricultural waste, where more data are available
from full-scale applications. These are point-sources and more
concentrated, making the recovery potential from them higher. The
possibility of combining measures for diffuse and point sources has
been considered, however the combination would be too difficult and
possibly not meaningful in a systems analysis with aim and scope as
this. In all catchment areas, stormwater management and pollution
were an issue, but few ecotechnologies for recovering nutrients or
carbon from stormwater have been identified in WP2. Therefore,
management of stormwater is not included in any system
alternative.
2.6 Assessment of the sustainability criteria
For the Vantaanjoki catchment area it was decided that resource
recovery from mainly agricultural wastes and residues was to be
assessed (described in detail in chapter 3). Three systems were
assessed containing the following main ecotechnologies: composting,
anaerobic digestion, pyrolysis, source-separation at on-site
wastewater systems and blackwater hygienization. In the Fyris and
Słupia catchment areas domestic wastewater was the focus. Similar
systems were set up for Fyris and Słupia (described in detail in
chapters 4 and 5), therefore the same criteria were used for both
case-studies. For each of these two case-studies, four system
alternatives were assessed. The main ecotechnologies included were:
conventional treatment and anaerobic digestion of sludge
(baseline), ammonia stripping, struvite recovery, anaerobic
treatment of wastewater, phosphorus extraction from sludge
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incineration ashes and source-separation. All criteria assessed
in this report are presented in Table 2, including which
case-studies they were used in. Each criterion is described below.
Table 2. The sustainability criteria used for each case study.
Sustainability criteria Vantaanjoki Fyris Słupia
Global warming potential X X X Eutrophication potential X X X
Nutrient recovery X X X Total costs X X X Effects on soil structure
X Impacts on local economy X Acceptance X X X Risk of exposure to
pollutants X X X Compatibility with existing infrastructure X
Technical robustness X X Technical flexibility X X
Global warming potential is calculated as the systems net
emissions of CO2 equivalents. There are several inputs to the
systems in the form of electricity, heat and chemicals. In the
systems, several sources of greenhouse gas emissions can occur such
as from transport or from the treatment processes. Emissions from
spreading and use of fertilizers are not included in the greenhouse
gas calculations. The reasoning behind this is that we assume that
the new fertilizer products replace mineral fertilizers, so in
total no more fertilizers are used in agriculture compared to
previously. Most greenhouse gas emissions from use of fertilizers
(nitrous oxide) are connected to nitrogen load and as the nitrogen
load will be the same we can assume that the greenhouse gas
emissions will be similar. This is of course a simplification, as
emissions of indirect nitrous oxide emissions also occur, however
we think this simplification will not matter greatly for the
interpretation of the results. The systems can provide benefits and
products which replace other resources, thereby “saving” emissions.
An example is replacing mineral fertilizer with recovered
nutrients. This constitutes a negative emission for the system, and
so the net emissions are reduced accordingly. More detail on which
processes and emissions that are included in the global warming
potential calculation for each case study is found in chapters 3, 4
and 5. Eutrophication potential was assessed through a similar
modelling as was done to calculate global warming potential for
Fyris and Słupia. The indicator for this criterion was PO43-
equivalents, calculated with the CML method (Heijungs et al.,
1992). The calculated eutrophication potential is a “worst case”
scenario where all emissions of nitrogen and phosphorus contribute
to eutrophication. The sources of PO43- eq. in these cases were
nitrogen and phosphorus released directly to water, air emissions
of ammonia and NOx emissions from transports. For the Fyris and
Słupia cases, eutrophying emissions from soil which has received
fertilizer is not accounted for. The system boundary ends where the
fertilizer is applied to the soil. For the Vantaanjoki case the
assessment of this criterion was done qualitatively based on
nutrient leakage using early modelling results from WP4. The
nutrient recovery criterion was based on substance flow
calculations of nitrogen and phosphorus recovered and returned to
agriculture in each system. The criteria effects on soil structure
were based on substance flow calculations of the amount of carbon
returned to agriculture in each system. The total costs calculated
included costs for investments, maintenance and operation. The
investment
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costs included for example costs of reactors and construction of
facilities. Annual capital cost was calculated with the annuity
method, using 3% interest. The maintenance cost was calculated as
3% of the total investment cost. The operations costs included
costs for energy, chemicals, staff, etc. Revenues for fertilizer
products and surplus energy produces were subtracted, resulting in
a net cost for the system studied. In Vantaanjoki, the criteria
impacts on local economy was applied assessing the pros and cons of
the different alternatives for the people who lives or have their
businesses within the catchment area. The criterion acceptance was
qualitatively based on the general acceptance of using the
recovered nutrient products as fertilizers in agriculture. This
criterion was assessed by stakeholders at the second workshop for
the Fyris and Słupia case-studies. For the Vantaanjoki case study,
acceptance was based on a local study of acceptance in the area.
Risk of exposure to pollutants was assessed based on the content of
heavy metals, pharmaceuticals, microplastics and visible
contaminants in the fertilizer products and possible other outputs
produced in the systems. The compatibility with infrastructure
criterion was assessed by local stakeholders at the second workshop
in the Vantaanjoki catchment area. Technical robustness was
assessed based on the systems risk for operational stops,
sensitivity for overflows and severity of consequences if either
were to occur. Technical flexibility was assessed based on the
systems flexibility to changes in load, due to increase or decrease
in population, and ability to adapt to new technologies or new
treatment requirements. Data for calculations were firstly
collected from local sources, such as wastewater treatment plants
or national institutes. Secondly, scientific literature and
previous projects were used for data acquisition. If no data were
found, estimations and assumptions made by experts were used.
Quantitative criteria were evaluated for the systems based on
literature, expert knowledge and in some cases the opinions of
local stakeholders. For each system, each criterion was given a
score based on the systems performance in that sustainability
aspect. The score given was between -2 and +2, where +2 is highest
performance and -2 is poorest performance. Each case study had one
system alternative representing the baseline system; this system
was given the score 0 for all criteria. The other systems were then
given a score higher or lower depending on whether the performance
on the criterion in question was higher or lower than that for the
baseline system. The criteria global warming potential,
eutrophication potential, nutrient recovery and total costs were
scored based on the following: Over 40% worse than baseline: score
-2 Up to 40% worse than baseline: score -1 Within 20% of baseline:
score 0 Up to 40% better than baseline: score 1 Over 40% better
than baseline: score 2
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Important to keep in mind is that the score 0 does not mean that
the performance of the system regarding the criterion in question
is 0. For example, if the baseline is given the score 0 for Total
costs this does not mean that the costs are 0; it means that the
cost for the baseline system has a middle value. The performance of
the baseline system is neutral in comparison to itself. The other
systems are compared in relation to the performance of the baseline
system. So, a system alternative that has a 30% higher total cost
than the baseline system is assigned the score -1. At the second
workshop, the main aim was to assign weights to the different
criteria. This was done by the local stakeholders participating at
the one-day workshop. Participants were divided into groups and
asked to first individually give weights to the previously
mentioned criteria so that the sum of weights was 100. After
individual weighting, each group’s facilitator collected the
individual weightings and typed them into an Excel-sheet where
group averages were calculated. The group averages were then
discussed within the whole group and changed in consensus if
necessary. Another purpose of the workshop was to get input on
locally anchored criteria where stakeholder opinions were of great
importance for the score. When all criteria were scored and weights
assigned, a weighted sum was calculated for each system with
equation (1). The result was an overall sustainability score for
each system to be compared to the others. 𝑇𝑜𝑡𝑎𝑙 𝑠𝑐𝑜𝑟𝑒 = ∑ 𝑤𝑒𝑖𝑔ℎ𝑡𝑖 ×
𝑐𝑟𝑖𝑡𝑒𝑟𝑖𝑜𝑛𝑖
𝑛𝑖=1 (1)
In equation (1), weighti is the weight assigned to the criterion
i and criterioni is the score assigned to criterion i.
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3 MULTI-CRITERIA ANALYSIS IN THE VANTAANJOKI CASE
For the Vantaanjoki case study, the focus was the agricultural
sector with an addition of source-separated blackwater from
scattered settlements (on-site sewage systems). Residual flows from
agriculture studied as input biomass for alternative systems was
horse manure and non-utilized grass such as set-aside grass and
buffer zones grass. The substrates (horse manure, grass and source
separated blackwater) were all discussed by local stakeholders as
potentially interesting for resource recovery, see actual
quantities presented in Table 3. The case study consisted of three
different system alternatives (see chapter 3.1 below, for
description and illustration of each system alternative):
1. Composting
2. Anaerobic digestion
3. Pyrolysis + urea hygienization of source-separated
blackwater
Table 3. Quantities of biomass used as input for the system
alternatives in the Vantaanjoki case study
The sustainability criteria used for the assessment are
presented in the previous chapter 2.6.
3.1 System alternatives
For all system alternatives horse manure and grass are collected
and transported to a centrally located plant co-located with the
waste incineration plant in Vantaa. In system alternative 1.
Composting and 2. Anaerobic digestion, also source-separated
blackwater is treated in a central facility in Vantaa. For system
alternative 3. Pyrolysis + urea hygienization of blackwater, the
source-separated blackwater is treated locally in 32 basins for
urea hygienization placed on farms with very short or no distance
to the fields. 1. Composting was the baseline system, against which
the other two systems were compared.
3.1.1 System alternative 1: Composting
In this system alternative, horse manure and grass are
co-composted with 23% of the source-separated blackwater. The rest
of the collected blackwater is treated in a thermal hygienization
unit. All treatment is done in one central plant located in Vantaa.
The system is illustrated in Figure 1. The solid feedstock, horse
manure and grass for composting, is crushed in a shredder, then
blackwater is added to achieve appropriate dry matter content.
After that, the material is fed into a reactor composting step. The
main function for the reactor composting, is to ensure that the
mixture is hygienized and to generate the heat (60oC) to hygienize
the source-separated blackwater. The
Biomass Tonnes/year tonnes dry matter/year
N (tonnes/year)
P (tonnes/year) C (tonnes/year)
Horse manure 35 000 12 157 172 35 5 471 Grass, set-aside 33 993
10 198 255 71 4 691 Buffer zone grass 4 177 1 253 21 5 564
Blackwater 63 887 375 93 11 164
Sum 137 057 23 983 541 122 10 890
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retention time in the vessel is about seven days. Air is
supplied to ensure that aerobic conditions exist in the whole
compost pile. The temperature in the composting material is
expected to reach 60oC within two days, then the amount of supplied
air is adjusted to retain that temperature. The air leaving the
vessel will also be close to 60oC and saturated with moisture and
is passed through a heat recovery step. The temperature of the
compost air falls in the heat exchanger and a condensate water is
generated. Most of the recovered heat from the compost air comes
from this condensation. Condensate water is collected in a storage
tank and used as nitrogen fertiliser. The compost air from the
vessel is treated in a biofilter to reduce odours, before
atmospheric dispersion. Most of the ammonia emissions will be
trapped in the condensate water. The recovered heat is mainly used
for the thermal hygienization unit, where the source-separated
blackwater, that is not used in the substrate mix, is heated to
53oC with a guaranteed retention time of 15 hours in the
hygienization chambers, operated batch-wise. Excess heat is assumed
to be used for heating buildings at the composting plant. After
reactor treatment, the composted material goes for post-composting
treatment in turned windrows for approximate four weeks. Afterwards
the compost is shredded and moved to an area for compost maturing
and storage. The matured compost is used as soil
conditioner/amendment. Hygienized blackwater is spread as liquid
fertilizer or used as nutrient irrigation on agricultural land.
Figure 1. Illustration of system alternative 1: Composting,
where horse manure, grass and blackwater undergo reactor composting
in one centrally located plant. The unused blackwater is treated in
a thermal hygienization unit.
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3.1.2 System alternative 2: Anaerobic digestion
In this system alternative, horse manure, grass and part of the
collected blackwater undergo anaerobic digestion with production of
biogas and digestate. Horse manure and grass are co-digested with
57% of the source-separated blackwater. The rest of the collected
blackwater is treated in a thermal hygienization unit. All
treatment is done in one central plant located in Vantaa. The
system is illustrated in Figure 2. The solid substrate is, after
weighing, received on a concrete slab which provides capacity for
short term storage up to five days. It is then fed into the
pre-treatment equipment by a wheel loader. Pre-treatment consists
of cutting equipment in order to simplify material handling and to
improve digestibility. Incoming source-separated blackwater enters
a short-term liquid storage and is divided into two streams. The
main stream is pre-heated with recovered heat from digestate (see
below) and mixed with the solid substrate in proportions resulting
in an appropriate humidity for dry fermentation (approx. 22% DM).
The mix is fed into plug-flow digesters operated at thermophilic
temperature (55°C) where biomass will decompose anaerobically,
resulting in the formation of raw biogas. The high operating
temperature together with a verified minimal retention time due to
the plug-flow setup ensures the hygienization of the material. The
remaining material after digestion (digestate) leaves the digesters
after a retention time of 25-30 days and is fed into a dewatering
step producing a solid and a liquid fraction. The solid fraction is
stackable and contains the majority of phosphorus from the
substrate. It is stored on a concrete slab and is transported to
external long-term storage facilities and can be used as fertilizer
since it is rich in phosphorus and fibres. The liquid portion of
the digestate passes a heat exchanger for the recovery of some heat
energy used to pre-heat incoming source-separated blackwater and/or
substrate mix. Finally, it enters the short-term liquid digestate
storage which is a concrete or steel tank with gas tight roof.
Minor amounts of biogas may be formed in that storage and will be
led to the digesters’ gas system. The source-separated blackwater
not used in the substrate mix is fed into a separate hygienization
unit consisting of three chambers operated batch-wise. The water is
first pre-heated by heat exchange with water leaving the unit, and
then heated to 70°C. It is further fed into one of the chambers
where it remains for 1 hour at controlled temperature (70°C).
Finally, it is pumped out of the hygienization chamber and through
a heat exchanger where heat is recovered and used to preheat the
next batch of blackwater, and then fed into a concrete vessel with
roof acting as short-term storage for outgoing blackwater.
Hygienized blackwater is spread as liquid fertilizer or used as
nutrient irrigation on agricultural land. Formed biogas from the
main digesters as well as the liquid digestate storage enters a gas
upgrading plant where unwanted components such as carbon dioxide,
hydrogen sulphide and water vapor are removed. A chemical scrubber
using amines is applied which provides large amounts of excess heat
used to heat the digesters and hygienization of source-separated
blackwater. Finally, the upgraded biomethane is compressed and fed
into the natural gas grid.
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Figure 2. Illustration of system alternative 2: Anaerobic
digestion, where horse manure, grass and source-separated
blackwater undergo anaerobic digestion with production of biogas
and digestate in a centrally located plant. The unused blackwater
is treated in a thermal hygienization unit.
3.1.3 System alternative 3: Pyrolysis + urea-hygienization of
source-separated blackwater
In this system alternative, horse manure and grass are converted
to biochar by pyrolysis, a chemical transformation at high
temperatures in an oxygen-free environment, in a central plant.
Since a prerequisite for the pyrolysis process is dry material, no
source-separated blackwater is added but instead treated locally in
covered basins by adding urea for hygienization, see Figure 3. For
pyrolysis to occur, high temperatures are needed, in this case
700°C. The input material therefore needs to be dry, here estimated
as 95% dry matter. The pyrolysis process generates char, gas and
tar. The distribution between these products can be controlled by
the pyrolysis temperature and retention time. In this case, the
process is optimized towards char production. Typical product gases
from pyrolysis (syngas) are CO, CO2, H2, CH4, N2 and other light
hydrocarbons. These are incinerated for heat production which
primarily is used to run the process and drying of biomass. Excess
heat can be used in district heating. Flue gas cleaning to meet the
limit values for current legislation is installed. The drying step
is energy-intensive and heat-demanding, since the dry matter of
incoming biomass is only 30-35% DM. Measures such as letting grass
pre-dry on fields, with a potential to increase dry matter up to
70%, would for example radically change the energy balance.
Generally, phosphorus will be recovered in the biochar (tightly
bound) and most of the nitrogen will be converted to gas phase
during the pyrolysis process. However, nitrogen from horse manure
may partly be released as ammonia during drying; a process for
utilizing nitrogen from condensate is
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therefore included in the alternative. Biochar is primarily used
as soil improver in agricultural land. Benefits seen are also
storage of biogenic carbon and recycled phosphorus as stored
fertilizer. When adding urea to blackwater it becomes NH3 that,
together with increasing pH, is toxic to pathogens. In this
alternative, it is assumed that source-separated blackwater is
treated with liquid urea (1%) in 32 containers with a volume of
2000 m3 each. The containers are built with waterproofing cloth
(including an external filling/emptying well)1, and with a floating
blanket to prevent emission of ammonium. For mixing, a
tractor-driven propeller stirrer with protective carriage are used.
The containers are locally placed on farms so the hygienized
blackwater can be spread on nearby fields. The 32 basins are placed
in areas with many septic tanks or geographically in the catchment
area so that transport can be minimized. The transport from a
septic tank to a local container is calculated based on data about
areas with high numbers of septic tanks, geographical location of
fields, the size of transport vehicles (12 m3) and the approximate
size of septic tanks in Finland (10 m3). Since urea increases the
nitrogen content in the blackwater, it is usually used as a
nitrogen fertilizer. Due to the high amount of water (0.6% DM) it
can also be used as nutrient irrigation.
Figure 3. Illustration of system alternative 3, where horse
manure and grass are converted to biochar by pyrolysis in a
centrally located plant and source-separated blackwater is treated
locally by urea hygienization.
1 Information about the intended product types can be found at
MPG Miljöprodukter AB (https://www.mpg.se/)
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3.2 System boundaries and assumptions
The system boundaries of the calculations of global warming
potential are presented in Figure 4. The climate impact
calculations start with the treatment of biomass. The cultivation,
harvesting and collection of the biomass are not included, as we
focus here mainly on comparing different treatment options and we
have the same amount of input biomass in each scenario.
Figure 4. System boundaries for calculation of global warming
potential in the Vantaanjoki case study.
The products that come out of the treatment are used as
fertilizers and soil amendments on arable land. For products
containing nitrogen and phosphorus, we assume they can replace
mineral fertilizer alternatives, giving the systems a climate
credit by reducing the emissions from mineral fertilizer
production. In the pyrolysis case, most nitrogen will be lost.
However, in the pyrolysis scenario, the blackwater is treated with
urea and the urea together with the blackwater is spread on the
fields. The urea is however not seen as a credit to the system as
it is an external input and does not mean a reduced use of mineral
fertilizers. Systems that generate surplus energy such as heat and
biogas fuel will be credited the replacement of other energy, e.g.
biogas can replace natural gas. For biochar, there is no
replacement product; we assume that biochar will increase soil
carbon content giving a climate benefit of carbon sequestration. Of
the carbon that is applied to fields, only a share is transferred
to the long-term soil carbon pool. In this study we assumed 15% of
the carbon in compost and digestate becomes stable soil carbon and
is given climate credit. For blackwater we assume 5%, and for
biochar 30%. A higher soil carbon content could lead to higher
yields, especially in degraded soils. However, the effects in
northern Europe are uncertain and therefore we did not include
potential yield improvements in this study. Transport distances
were estimated based on maps of the Vantaanjoki region in
combination with occurrences of activities in different areas of
the region. The estimated distances are presented in
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Table 4. Transport emissions were modelled to include positions
of empty truck and empty return (by assuming a load factor of 50%
and double distance) and with GHG emissions data from Network for
Transport Measures (NTM Calc, 2019). Transport was assumed to be
carried out with rigid trucks with varying capacities between 7 and
26 tons. Table 4. Estimated transport distance for the different
substrates and products in the Vantaanjoki area.
Transport type Distance
Grass from set-aside fields to central treatment
(compost/AD/pyrolysis) 35 km
Buffer zone grass to central treatment (compost/AD/pyrolysis) 30
km
Horse manure to central treatment (compost/AD/pyrolysis) 26
km
Blackwater to central heat treatment (compost/AD) 27 km
Solid fertilizer products to field (compost, solid digestate,
biochar) 27 km
Liquid fertilizer products to field (liquid digestate,
heat-treated blackwater) 10 km
Blackwater to urea treatment 6 km
Blackwater from urea treatment to field 0 km
The total annual cost for the system alternatives was calculated
using the annuity method. The revenue from selling biogas was
included but not for other residuals such as biochar, or fertilizer
products. The total costs for the composting, anaerobic digestion
and blackwater hygienization were based on data from earlier
applications while data for the pyrolysis plant was based on
information from a company that deliver these plants. General
Finnish data were collected for energy and transport costs.
3.3 Results
3.3.1 Global warming potential
The results of the modelling are presented in Figure 5. As can
be seen, each scenario has both contribution to global warming as
well as climate benefits/credits. These contributions consist of
process emissions and transports. The process emissions include
electricity use, but for the composting and anaerobic digestion
alternatives, process emissions come mainly from storage of
compost/digestate. Regarding climate benefits, we can see that soil
carbon, i.e. carbon sequestration by applying organic fertilizers
has a large impact on the net emissions. Replacement of mineral
fertilizers also contributes to benefits; where recovered nitrogen
plays the major role as mineral nitrogen fertilizer production
produces considerable greenhouse gas emissions. The production of
biogas which replaces natural gas constitutes a large climate
benefit for the anaerobic digestion system.
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Figure 5. Results for GHG-calculations of Vantaanjoki region
scenarios. FU= Functional unit, in this case treatment of 137 057
tons biomass per year. Numbers above each bar are the total
value.
The scores for global warming potential are: 1. Composting 0 2.
Anaerobic digestion 2 3. Pyrolysis + urea hygienization 2
3.3.2 Total costs
The result of the costs analysis showed that the Composting
alternative has an annual cost of 3 MEuro, while Anaerobic
digestion actually has such a projected revenue from selling biogas
that the alternative ends up with a negative cost of 1 MEuro (i.e.
a yearly profit of 1 MEuro). This means, the anaerobic digestion
alternative is economically more effective than composting, despite
having higher maintenance/investment costs in our assessment. The
pyrolysis alternative had the largest cost: 8 MEuro. This may be
due to fact that the cost estimation is based on data from smaller
pyrolysis plants (a number of plants are built in parallel in the
system alternative). Considering economy of scale, the estimated
costs could be overestimated for the pyrolysis plants.
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The scores for Total costs are: 1: Composting 0 2: Anaerobic
digestion 2 3: Pyrolysis + urea hygienization -2
3.3.3 Eutrophication potential
For the assessment of eutrophication potential, both diffuse and
point-source emissions were considered. In terms of agricultural
residues, eutrophication potential can be decreased if more
residues from buffer zones and green fertilizing (crop rotation)
are incorporated into the arable soils of the Vantaanjoki
catchment. Thereby the soil structure will become more resilient to
surface runoff and erosion and particle-bound P loading will thus
decrease. Moreover, the increased carbon content of soil will
enhance denitrification which, in turn, will decrease N loading.
This process was clearly demonstrated by the first SWAT scenario
simulations, where 50% increase of soil carbon (% of weight unit)
led to 10% decrease in total N loading (upcoming project
deliverable D 4.4).
Horse management, particularly in larger stables, may induce
point-source type nutrient loading, which could be alleviated by
wise utilization of the energy and fertilization potential of the
horse manure. When applied to arable land and used instead of
mineral fertilization, horse manure may decrease nutrient loading
for the same reason as in the case of plant residues, i.e. by
improving the soil structure. Because of a lower amount of carbon
to soil, anaerobic digestion received a lower score than the other
alternatives. The scores for Eutrophication potential are:
1. Composting: adds 8012 tonnes of C to soil/year 0 2. Anaerobic
digestion: adds 4872 tonnes of C to soil/year -1 3. Pyrolysis +
urea hygienization: adds 5527 tonnes C to soil/year 0
3.3.4 Nutrient recovery
The indicator chosen was the recycling of nitrogen and
phosphorus (tonnes/year). The major part of phosphorus is recycled
in all alternatives, and almost all nitrogen is recycled in
alternatives 1 and 2. Only 80% of phosphorus and 17% of nitrogen is
recycled in alternative 3. The scores for nutrient recovery
are:
1. Composting (122 tonnes P, 550 tonnes N per year) 0 2.
Anaerobic digestion (122 tonnes P, 540 tonnes N per year) 0 3.
Pyrolysis + urea hygienization (99 tonnes P, 93 tonnes N per year)
-2
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3.3.5 Risk of exposure to pollutants
The criterion risk of exposure to pollutants, includes a
discussion around the content of heavy metals, pharmaceuticals,
microplastics2 and visible contaminants3, both in the incoming
substrates and in the treated fertilizers. The risk of pollutants
in the fertilizer depends on the content in the incoming substrates
and whether these pollutants are retained, transformed or lost in
the process. Agricultural residues and horse manure generally have
a low content of pollutants. The agriculture residues may be
affected by pollutants in the soil or air, and by foreign objects
which may have landed on the fields (source for any visible
contaminants). The horse manure composition may be affected by
various sources in the stables, such as bedding material, stable
furnishing and human impact and objects that follows when
collecting the horse manure (for example stones, rope and metal
objects). Pharmaceutical residues may be the result of medicating
the horses, and visible contaminants and microplastics can be
present in the horse manure as a result of the use of plastic for
conservation of silage. Source-separated blackwater can contain
pharmaceutical residues from our intake of medicines. Visible
contamination is not expected in blackwater, however, there is a
risk that for example ear swabs, sanitary napkins and tampons are
flushed down the toilet. There is also a risk of general
contamination from the trucks transporting the blackwater, if they
are not washed between uses. The composting and the digestion
processes are not expected to contribute to additional pollutants,
although degradation of pollutants by bioremediation can generate
new hazardous byproducts in the form of metabolites. Little
degradation of microplastics and pharmaceuticals are expected, but
fragmentation of visible contaminants can occur (e.g. fragmentation
of plastic particles into microplastics). In the pyrolysis process,
hormones, pharmaceuticals and other organic compounds be degraded.
It is also possible at high temperatures to remove heavy metals,
for example cadmium. Adding urea as a hygienization process is not
expected to affect the incoming content of pollutants. This means
that the biochar will have a lower risk for pollutant content than
the other fertilizer products. Though, looking at the system
alternatives including urea hygienization, the risk for
source-separated blackwater is similar in all alternatives. The
scores for risk of exposure to pollutants are:
1: Composting 0 2: Anaerobic digestion 0 3: Pyrolysis + urea
hygienization 1
2 Plastic particles < 5 mm. Definition from The Swedish
Environmental Protection Agency: " by humans made polymers from
either oil or by-products from oil, or from biomaterials (bio-based
sites)". 3 Foreign objects such as plastic, glass, metal and
composite materials with a size > 2 mm. Note that there is
overlap between "visible contaminants" and "microplastics" since
the limit for visible contaminants is> 2 mm and
microplastics
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3.3.6 Effects on soil structure
For this criterion it was assumed that addition of carbon to
agricultural soil improves the soil structure. Because of a lower
amount of carbon additions to soil, alternative 2 got a lower score
than the other alternatives. The scores for effects on soil
structure are:
1. Composting: 8012 tonnes C/year 0 2. Anaerobic digestion: 4872
tonnes C/year -2 3. Pyrolysis + urea hygienization: 5527 tonnes
C/year 0
3.3.7 Acceptance of using recycled fertilizer products
This criterion assesses stakeholder acceptance for spreading
recycled products on farmland. A study on the acceptance of using
wastes as fertilizers was conducted in Finland in 2018. The study
found that farmers had a more negative opinion towards the use of
sewage sludge and other products with origin from human excreta
compared to food waste and agricultural waste (Myllyviita &
Rintamäki, 2018). Across the three system alternatives, it is
assumed that treated horse manure, grass and blackwater are spread
on farmland. In the pyrolysis alternative, agricultural wastes are
not mixed with blackwater which means that the products generated
from human excreta can be handled separately if so wanted. The
scores for acceptance of using recycled fertilizer products
are:
1: Composting + heating of BW 0 2: Anaerobic digestion + heating
of BW 0 3: Pyrolysis + urea hygienization 1
3.3.8 Local economy
This criterion assesses the potential for creating new
businesses in Vantaanjoki area. All the suggested alternatives will
be adding new activities i.e. collection of horse manure, grass and
blackwater, and treatment, storage and recycling of products on
farmland. In the pyrolysis alternative, the blackwater treatment is
decentralized in 32 places which means more activities within the
catchment area. The scores for local economy are:
1: Composting + heating of BW 0 2: Anaerobic digestion + heating
of BW 0 3: Pyrolysis + urea hygienization 1
3.3.9 Compatibility with existing infrastructure
Vantaa is the location of the centralized process facility and
it is assumed that the facility is newly built for all the
alternatives. This is 1) to have access to professional operations
and maintenance staff, 2) so that heat use and excess heat produced
can be integrated with the existing Vantaa heating plant.
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In the second workshop the stakeholders considered that less
traffic in the Vantaa area would be prioritized and therefore they
gave alternative 3, which includes decentralized blackwater
treatment a higher score. The scores for Compatibility with
existing infrastructure are:
1: Composting + heating of BW 0 2: Anaerobic digestion + heating
of BW 0 3: Pyrolysis + urea hygienization 1
3.3.10 Second workshop in Vantaanjoki
Participants were divided into three groups. To start with, they
individually gave weights to the previously mentioned 9 criteria so
that the sum of weights had to be 100. The 3 group averages were
then discussed within the whole group and adjusted through
consensus if necessary. The results of the three groups varied. The
results by criterion categories are shown in Table 5. Table 5.
Weights assigned by the three groups and the average weights for
the Vantaanjoki case study.
Criteria Group 1 Group 2 Group 3 Average
weight
Global warming potential 21 10 18 16
Eutrophication potential 5 5 4 5
Effects on soil structure 8 10 20 13
Nutrient recovery 5 5 6 5
Local economy 8 5 7 7
Total costs 16 25 9 17
Acceptance 13 15 12 13
Risk of exposure to pollutants 10 15 13 13
Compatibility with existing infrastructure
14 10 11 11
3.3.11 Sustainability scores for all systems
In the scoring, the composting alternative was set as the
baseline with score 0 for all criteria. The final scores are
presented in Table 6.
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Table 6. Scores for each criterion for each system alternative
for the Vantaanjoki case study.
Criteria Composting Anaerobic digestion Pyrolysis + urea
hyg.
Global Warming potential 0 2 2 Eutrophication potential 0 -1 0
Nutrient recovery 0 0 -2 Effects on soil structure 0 -2 0 Local
economy 0 0 1 Total costs 0 2 -2 Acceptance of using recycled
fertilizer products 0 0 1
Risk of exposure to pollutants 0 0 1 Compatibility with
infrastructure 0 0 1
Based on the average of weights from Table 5, the weighted sum
of the three alternatives was calculated in Figure 6. The results
show that alternative 2, Anaerobic digestion got the highest
weighted score followed by alternative 3, Pyrolysis. Alternatives 2
and 3 reach almost the same sum but considerably higher than
alternative 1, Composting. Both alternatives 2 and 3 have a large
advantage compared to alternative 1 because of a lower impact on
climate change. Alternative 3, Pyrolysis, also has other strengths
in terms of local economy, acceptance, risk of exposure to
pollutants and compatibility with infrastructure. Alternative 3
has, however, one disadvantage which is the considerable annual
costs.
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Figure 6. Total sustainability score for each system alternative
in the Vantaanjoki case study. The error bars show the scores based
on the different weighting of criteria from the three stakeholder
groups at the second workshop.
3.4 Discussion of results
For the Global warming potential, soil carbon had a major
influence on the results because carbon is sequestered in the soil
and thereby contributes to a reduction in global warming. However,
soil carbon dynamics are complicated and depend on many
site-specific factors such as soil properties and temperature. The
climate benefits must therefore be interpreted with great caution.
Biochar has in the literature been pointed out as being especially
promising for carbon storage. However, there are large variations
in the conclusions reached in the literature regarding carbon
storage potential. Pyrolysis conditions alter the properties of the
biochar and carbon storage ability, and so does the pyrolysis
feedstock and the type of soil where the biochar is added. More
in-depth site-specific analysis and soil carbon modelling are
needed to draw accurate conclusions. For the compost and anaerobic
digestion alternatives, processing and storage make up the majority
of the emissions. During the drum composting and storage, emissions
of ammonia, methane and nitrous oxides can occur. For anaerobic
digestion, we include emissions from storage of liquid and solid
digestate and from leakage of methane during biogas upgrading.
However, the positive side is that these emissions can be reduced
through improved processes or handling and storage, e.g. by
covering tanks and reducing the storage time.
The high weights participants assigned to environmental impacts
were justified e.g. by the fact that the idea behind circular
economy is to reduce the environmental impacts and make the economy
more sustainable. On the other hand, high weights on economic
impacts were justified by the large impact
0
10
20
30
40
50
60
1. Composting 2. Anaerobic digestion 3. Pyrolysis+urea hyg.
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range in total costs, and the overall importance of the economic
impacts. If the benefits and costs are not balanced, the measures
won’t be feasible. However, in one group, a strong opinion was
stated that the environmental impacts are so crucial that
regardless of costs, actions must be taken. Eutrophication received
the lowest weights in all groups for two main reasons; i) the
improved soil structure was seen to decrease nutrient loading
already, and ii) the impact range between the ecotech-alternatives
was small and the assessment uncertain. The acceptance and the risk
of exposure to pollutants were seen to be connected to each other,
and the participants (at least in Group 2) thought that these
impacts together have enough weight even though the weight is
divided between the criteria. Technical feasibility was seen as
least important. In general, participants thought that blackwater
should not be mixed with agricultural residues in any of the
alternatives. This would improve the performance of compost and
digest compared to the pyrolysis option. In addition, at least some
participants considered that also composting and anaerobic
digestion would be maybe more feasible in the decentralized
option.
3.5 Conclusions
In the Vantaanjoki case study, the system alternative with
anaerobic digestion of substrates got the highest sustainability
score using average weights from the stakeholder workshop. However,
the pyrolysis of horse manure and grass and urea hygienization of
blackwater got almost as high score. Both these alternatives got
much higher scores than the alternative with composting, which was
the baseline system. This suggests both of these alternatives are
more sustainable options than the composting alternative.
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4 MULTI-CRITERIA ANALYSIS IN THE FYRISÅN CASE
In the Fyrisån catchment area, different technical systems for
recovering nutrients and energy from domestic wastewater were
assessed. The sustainability criteria used in the assessment are
described in chapter 2.6. In all system alternatives, the same
amount of wastewater is treated, i.e. the systems perform the same
functions.
4.1 System alternatives
4.1.1 Alt 0F Baseline
The baseline system (Alt 0F: Baseline) represents the
conventional wastewater treatment currently in use in the area.
Figure 7 shows a flow chart for the system. For this alt